As well-known, feeders have been used in many manufacturing fields or other fields. There have been various type feeders such as a belt-conveyor type feeder, a screw type feeder, a cylinder type feeder, a timing belt type feeder and a robot. Such feeders are also called conveyor systems or reciprocating apparatuses.
The belt-conveyor type feeder among the aforementioned feeders is inexpensive and suitable for long distance conveyance, but has a poor precision of positioning the conveyance things and a feeding velocity later than the other feeders. In addition thereto, the belt conveyor requires a large installation space proportional to the conveyance distance. The screw type feeder has the higher precision of conveyance because of the use of the polish ball screw and enables the conveyance at middle or high velocity. However, the expensive polish ball screw would cause the apparatus to get also expensive. The screw type feeder is not of space-saving type and also has a shorter conveyance distance, which makes the long distance conveyance difficult. The cylinder type feeder also has the difficulty of long distance conveyance and the problem of expensiveness in the same manner as the screw type feeder. Thus, this cannot accomplish the compactness, which is required for the space saving. Particularly, the cylinder type feeder has the practical problem in which it is difficult to arbitrarily change the conveyance stroke. On the other hand, the timing belt type feeder is more inexpensive than the screw type feeder using the polish ball screw, but gets more expensive than the belt conveyor if it employs highly precious parts in order to expect the high precision of positioning. In addition thereto, the timing belt type feeder can set the conveyance distance longer than the screw type feeder or the cylinder type feeder, but cannot maintain the conveyance distance identical to that of the belt conveyor due to the restrictions on manufacture or the looseness of the belt. Thus, the timing belt type feeder has the conveyance distance shorter than the belt conveyor even though the former is less elongated than the latter. On the other hand, the robot is too expensive even though it has the considerably high precision and functions. In addition thereto, the robot is not suitable for continuous and long distance conveyance.
As apparent from the foregoing, the conventional feeders have merits and demerits. There has been not developed an advantageous and useful feeder having only merits collected so as to be able to embody it.
Describing the conventional feeders such as the aforementioned ball screw type feeder and the timing belt type feeder in more details, these feeders have an unavoidable occurrence of fine dust (dust of micro m unit or less) caused by friction between the parts of the drive system. There are the fields in which the fine dust is not regarded as questionable and the fields in which the fine dust should be excluded. The fields requiring an extra-high cleanness among the latter fields are the ones of manufacture of liquid-crystal boards and semiconductors.
In order to avoid the occurrence of the fine dust, there have been employed means to heighten an abrasion resistance of the parts or to use grease for reducing the occurrence of the fine dust. Regarding the apparatus, there have been developed a linear servo-actuator having little fine dust occurrence portion as a non-contact power source having electromagnetism power employed. If these means are totally used, predetermined clean atmosphere can be held in the fields of manufacture requiring the extra-high cleanness. However, the linear servo-actuator is too expensive even though it has means good for avoiding the occurrence of fine dust. Therefore, it has been expected to develop means to be able to maintain the cleanness having the same degree as the linear servo-actuator or higher and also to be able to more highly reduce the cost in comparison with the linear servo-actuator.
The technique for reducing the occurrence of the fine dust for the feeder desirably expects all possible measures by multiple means unless the cost gets extremely higher. Since it can improve the yields of the products and reduce the cost for treating the default goods, it will totally improve the economical efficiency.
The precision working apparatus essentially requires the highly precise conveyance as apparent. Therefore, it is an important problem to meet the highly precise conveyance according to its use.
With respect to the feeders, it is also important to maintain the safety and prevent secondary damages by detecting unexpected accidents, which would possibly occur.
The inventor has proposed the following invention as the feeder, which can resolve the aforementioned problems. As apparent from the patent document No. 4 indicated below, the proposed feeder comprises a forward winder which can rotate forwardly and reversely, a reverse winder which can rotate forwardly and reversely, a forwardly winding liner body to be wound and rewound through the forward winder, a reversely winding liner body to be wound and rewound through the reverse winder and a reciprocating body to forwardly and reversely move by means of guide means when it is subject to a forward force or a reverse force. The proposed feeder is characterized in that the forwardly winding linear body to be held so as to be wound and rewound by the forward winder and the reversely winding linear body to be held so as to be wound and rewound by the reverse winder are connected to the reciprocating body, the forward winder on winding rotation and the reverse winder on rewinding rotation rotate in synchronism and phase with each other in the winding and rewinding directions, respectively, the forward winder on rewinding rotation and the reverse winder on winding rotation rotate in synchronism and phase with each other in the rewinding and winding directions, respectively, the amount of winding the forwardly winding linear body by the forward winder and the amount of rewinding the reversely winding linear body by the reverse winder are equal to each other and the amount of rewinding the forwardly winding linear body by the forward winder and the amount of winding the reversely winding linear body by the reverse winder are equal to each other. In addition thereto, a friction occurrence portion may be covered with a dust cover. According to such a proposed feeder, the requirements of positioning accuracy, long distance conveyance, remote conveyance, controllability, high precision feeding, high speed feeding, inexpensiveness, simplicity of construction, space saving, weight reduction, measure for dusting and safety for accident can be met in accordance with the peculiar constructions, functions and effect of the feeder.
In general, a rotary body rotating about a shaft supported at both ends makes its flexure and vibration smaller as the distance between bearings on which both ends of the shaft are supported is smaller so that the quiet and stable state of rotation (state of operation) can be attained. The rotary body having such a desirable state of operation provides an indefectible normal state of operation of relevant parts associated with the rotary body through linear bodies and so on. Thus, the reduction of the distance between the bearings is important for a plan of precision feeding and high precision feeding. This reduction of the distance is desirable because it can avoid a hugeness of the apparatus and also increase a life of the parts of the apparatus based on quietness and stability of the state of operation thereof.
The proposed feeder comprises the forward and reverse winders as the rotary bodies and therefore cannot accomplish the more precise or high-precise feeding unless the distance between the bearings of the rotary bodies is reduced in view of the aforementioned points. Particularly, in case where a winding drum for the forward winder and a winding drum for the reverse winder are axially shifted at the same time when they rotate in order to wind the linear body in an arranged manner, the resolution of this problem has been made difficult because the distance between the bearings should be larger by the amount of shifting of the winding drums. Thus, the proposed feeder is required to have another technical improvement in view of the prevention of enlargement of the distance.
In the proposed feeder, the linear body to be wound around the forward or reverse winder or rewound from the reverse or forward winder is guided in a predetermined direction. In this case, the linear body is required to be precisely wound around or rewound from the winding drums in an equal pitch. If this is not met, the amount of winding the linear body (the amount of rewinding the linear body) per one revolution of the forward or reverse winder has variation generated, which causes the difficulty of precise feeding. More extremely, the portions of the winding linear body adjacent to each other on the winding drum would be rubbed or superposed one on another. Furthermore, if excessive torsion power is imparted to the linear bodies, it would have earlier fatigue and destruction. The proposed feeder has no technical matters for resolving such a problem.
Patent Document 1: JP2002-340127
Patent Document 2: JP2002-372119
Patent Document 3: JP2003-311562
Patent Document 4: Laying-Open Gazette of JP Application No. 2004-272796